1. Field of the Invention
The present invention relates to a resin-encapsulated semiconductor device of a non-lead type called QFN or DFN, and a method of manufacturing the same, and more particularly, to an improvement of mounting reliability at a lead terminal portion.
2. Description of the Related Art
In recent years, demands have been made for high-density mounting of semiconductor components in order to respond to the reduction in size of electronic devices. Along with the demands, the semiconductor components have been more and more downsized and thinned. In addition to BGA and CSP packages, DFN and QFN semiconductor devices have been put into practical use as compact packages using a lead frame.
FIG. 6A is a rear view of a conventional DFN package. FIG. 6B is a cross-sectional view taken along the line A-A of FIG. 6A. In the DFN package, lead portions 13 and a semiconductor element mounted on a die pad portion 12 are encapsulated by an encapsulating resin 16, and the plurality of lead portions 13 and the die pad portion 12 are exposed from a rear surface of the package. The plurality of lead portions 13 is arranged on the rear surface of the package along two parallel lines to form external leads. The plurality of lead portions 13 is electrically connected to the electrodes on the surface of the semiconductor element 11 with metal thin wires 14 in the encapsulating resin 16.
The DFN package has an advantage that a mounting substrate can be reduced in mounting area because the plurality of lead portions 13 do not protrude outward from the encapsulating resin 16. Another advantage is that, by exposing the die pad portion 12 from the encapsulating resin 16, heat generated inside can be radiated efficiently to the outside. Note that, some DFN packages have another structure in which the die pad portion 12 is encapsulated in the encapsulating resin 16. A QFN package has a structure in which external leads are exposed from a rear surface of the package in four directions.
FIG. 7 is a top view of a frame after resin-encapsulation as seen from above. FIG. 8 is a cross-sectional view taken along the line B-B after cutting of the frame of FIG. 7. The following method has hitherto been employed (see, for example, Japanese Patent Translation Publication No. 2002-519848 (FIG. 7)). That is, as illustrated in FIGS. 7 and 8, the semiconductor elements 11 mounted on the respective die pad portions 12 of the frame are encapsulated with the encapsulating resin 16, and then the encapsulating resin 16 and the lead portions 13 are simultaneously cut along cutting lines by a rotary blade of a dicing device, thereby singularized into individual semiconductor devices as illustrated in FIG. 9.
In this type of resin-encapsulated semiconductor device, the individual semiconductor devices are obtained by cutting the cutting regions of the lead portions 13 with the rotary blade to separate from the frame after the resin-encapsulation. No plated layer 17 is, however, present on an end surface of the cut part of the lead portion 13, because the lead portions 13 are formed by cutting from the frame. Thus, when the semiconductor device is bonded onto a mounting substrate 20 such as a printed substrate with the use of solder 18, a solder fillet of the solder 18 is not formed on a side surface part of the lead portion 13 exposed from the resin-encapsulated part, with the result that the mounting strength may be reduced to lower the mounting reliability.
A description is given with reference to the drawings. FIG. 10 illustrates the lead portion 13 of the semiconductor device as an enlarged view of the circle illustrated in FIG. 9. On an end surface part of the lead portion 13 that is exposed from the encapsulating resin 16 by lead cutting, the plated layer 17 is not present, which is formed instead on another external surface of the lead portion 13. Thus, as illustrated in FIG. 11 as a schematic cross-sectional view enlarging the mounted state, when the semiconductor device is mounted onto the mounting substrate 20 by an adhesive such as the solder 18, the solder fillet is not formed at the end surface part of the lead portion 13, and hence the mounting strength is lowered.